1. Field of the Invention
The present invention relates to a transfer apparatus and, more particularly, to a transfer apparatus capable of cleaning and drying a wafer transfer means in an isolated space in a treatment system such as a semiconductor wafer cleaning system.
2. Description of the Related Art
In a semiconductor manufacturing process, a cleaning system is used to remove chemicals or impurities adhered to the surfaces of semiconductor wafers. In the cleaning system, a plurality of cleaning chambers each for accommodating a treatment bath, such as an ammonia treatment bath, a washing bath, or a hydrofluoric acid treatment bath, are arranged. Wafers as objects to be treated are placed on and held by a transfer means and transferred to or from each treatment chamber by the transfer means.
In the cleaning system, a cleaner is used as a means for removing treatment solutions or dust adhered to the transfer means. The cleaner removes treatment solutions or dust adhered to the transfer means and dries the transfer means by using cleaning nozzles and drying nozzles, respectively. This cleaner is generally constituted such that large numbers of cleaning nozzles and drying nozzles are arranged on a pipe having a length corresponding to the total length of the transfer means so that a portion, for holding objects to be treated, of the transfer means is entirely cleaned and dried at one time.
In this structure, however, since cleaning and drying are performed with the fixed cleaning nozzles and drying nozzles, a cleaning solution and a drying gas are sprayed from a large number of nozzles at the same time. Therefore, not only large quantities of the cleaning solution and the drying gas are consumed, but also the size of the cleaner is increased because a space occupied by the nozzles is large. In addition, it is complicated to manufacture a cleaner in which cleaning nozzles and drying nozzles are arranged throughout the total length of the transfer means, and it is also difficult to obtain a uniform spraying condition.
In the cleaning system, in order to prevent a leakage of an internal atmosphere to the outside, each treatment bath and the cleaner are surrounded by a housing. The housing has an opening portion through which wafers are transferred in and out. The opening portion is closed by a shutter so that the atmosphere inside the housing does not leak out of it. A drive unit for the shutter is generally located below the opening portion.
In this structure, however, wafers are transferred to and from treatment chambers having different atmospheres by the transfer means. Therefore, a chemical having adhered to the wafers or the transfer means in a pretreatment may drop into the opening portion or on the shutter during transfer. In addition, the chemical dropped inside the opening portion enters the shutter drive unit through a sealing portion and corrodes the drive unit.
Furthermore, dust produced in the shutter drive unit adheres to the sealing portion and sometimes enters the opening portion to contaminate wafers. This decreases the product yield of wafers.